Fluid cooling system

ABSTRACT

An apparatus for cooling one or more heat generating components comprises: a sealable enclosure defining a volume for containing a first coolant and one or more heat generating components; a conduit surrounded by the volume, the conduit enabling a second coolant to enter and leave the enclosure, the conduit providing a fluid-tight seal between the first coolant and the second coolant when the first coolant within the volume surrounds the conduit; and a pump within the enclosure configured to direct the first coolant to the conduit such that heat is exchanged between the first coolant and the second coolant.

FIELD OF THE INVENTION

The present invention relates to a cooling system and in particular, acooling system for electronic devices and boards. The cooling system mayprovide a sealed enclosure for housing heat generating components suchas motherboards, memory modules or servers that require active or fluidcooling.

BACKGROUND OF THE INVENTION

Many types of electrical component generate heat during operation. Inparticular, electrical computer components such as motherboards, centralprocessing units (CPUs) and memory modules may dissipate substantialamounts of heat when in use. Heating of the electrical components tohigh temperatures can cause damage, affect performance or cause a safetyhazard. Accordingly, substantial efforts have been undertaken to findefficient, high performance systems for cooling electrical componentseffectively and safely.

One type of cooling system uses liquid cooling. Although differentliquid cooling assemblies have been demonstrated, in general theelectrical components are immersed in a coolant liquid so as to providea large surface area for heat exchange between the heat generatingelectrical components and the coolant.

U.S. Pat. No. 8,467,189 describes a liquid submersion cooling systemthat cools a number of electronic devices within a plurality of casesconnected to a rack system. A housing is filled with a dielectriccooling liquid with heat generating electronic components submerged inthe dielectric cooling liquids. The rack system contains a manifold thatallows liquid transfer for multiple cases and a pump system for pumpingthe dielectric cooling liquid into and out of the rack. External heatexchangers allow the heated dielectric cooling liquid to be cooledbefore being returned to the rack. However, this requires a significantquantity of dielectric cooling fluid to be pumped into and out of eachcase in the rack. Furthermore, it is difficult to effectively direct orfocus the cooling fluid within each case, which may contain differentheat generating components, each having their own cooling requirements.

U.S. Pat. No. 8,014,150 describes the cooling of electronic modules inwhich a cooling apparatus is coupled to a substrate to form a sealedcomponent around an electronic device. Pumps are located within thesealed compartment so that dielectric fluid is pumped towards theelectronic device. Cooling occurs by changing the phase of thedielectric fluid from liquid to vapour, which then is caused to condenseas it rises towards a liquid-cooled cold plate that is fed by a secondfluid. However, this cooling system requires high pressure seals andmultiple cooling compartments within a case and so relativelycomplicated plumbing arrangements for the second cooling fluid.

Therefore, there is required a method and system that overcomes theseproblems.

SUMMARY OF THE INVENTION

In accordance with a first aspect there is provided an apparatus forcooling one or more heat generating components. The apparatus forcooling one or more heat generating components comprises:

a sealable enclosure, tank or case defining a volume for containing afirst (or primary) coolant and one or more heat generating components(e.g. electronic components);

a conduit or tube surrounded by the volume, the conduit enabling asecond (or secondary) coolant to enter and leave the enclosure, theconduit providing a fluid-tight seal between the first coolant and thesecond coolant (especially) when the first coolant within the volumesurrounds the conduit; and

a pump (or at least one pump) within the enclosure configured to draw,pump, force or direct the first coolant to the conduit such that heat isexchanged between the first coolant and the second coolant. The pumpwithin the enclosure enables the first coolant to be directed moreeffectively at the hot spots or specific heat generating regions withinthe enclosure. Having an internally circulating primary coolant meansthat it is easier to seal the system. The secondary coolant enteringinto the enclosure provides a more efficient heat transfer between theprimary and secondary coolants. This combination of features provides amore effective cooling system that can be operated more reliably. Thesealable enclosure may be sealed with a lid or hatch. This may beremovable to allow access to internally located heat generatingcomponents or boards. The lid and other parts of the enclosure mayincorporate one or more gaskets or seals and may be hinged or fullyremoved. Fixings, such as clamps, screws, latches or clasps may securelyclose the enclosure. The sealable or sealed enclosure may berack-mounted, for example. The enclosure may be a module for housingelectronic components, such as processors, motherboards, servers, memorymodules or computer equipment.

In accordance with a second aspect there is provided a cooling module orapparatus used to cool one or more heat generating components (e.g. amotherboard). The cooling module comprises an enclosure that is sealableor sealed and contains a volume or void that may be filled or partiallyfilled with a first coolant or fluid. The first coolant stays within thevolume (that also contains the component or components to be cooled) andis circulated by one or more pumps. A separate cooling circuit,incorporating a second coolant (that is kept separate from the firstcoolant), enables heat to be removed from the module. The second coolantmay enter the module, exchange heat with the first coolant and thenleave the module. The second coolant may itself be cooled beforereturning to the module.

In accordance with a third aspect, there is provided a cooling module orapparatus used to cool one or more heat generating components (e.g. amotherboard). The cooling module comprises an enclosure that is sealableor sealed and contains a volume or void that may be filled or partiallyfilled with a coolant or fluid. The coolant stays within the volume(that also contains the component or components to be cooled) and iscirculated by one or more pumps. The coolant is directed over aplurality of hot areas or hot spots (two or more) that form from the oneor more heat generating components. Preferably, separate pumps directstreams or jets of coolant over the hot spots within the module. Cool(or relatively cool) coolant may be pumped over the hotspots. Thecoolant may be cooled and drawn back in to the pump for recirculation.This may be used with or without the secondary coolant.

In accordance with a third aspect, there is provided a heat exchangerformed from a channel or duct having an inlet for receiving a firstfluid or coolant, which leaves the channel by an outlet. A second fluidor coolant passes through a pipe, channel or conduit within the channel.At least some if not most of the flow of the first fluid is parallelwith at least some if not most of the flow of the second fluid withinthe conduit. Heat may be exchanged between the first fluid and thesecond fluid. The conduit may be u-shaped, for example. Preferably, theheat exchanger operates within a module housing heat generatingcomponents. Preferably, the first fluid remains within an enclosure orhousing of the module, whilst the second fluid enters and leaves themodule without allowing it to mix with the first fluid.

A number of optional, preferable and/or advantageous aspects are nowdescribed with reference to many if not all aspects disclosed herein.Preferably, the pump may be further configured to direct the firstcoolant towards the one or more heat generating components. This mayinclude one or more nozzles or vents to adjust the direction, speed,rate, pressure, width and/or height of flow of the first coolant withinthe enclosure. The pump may be provided upstream from the location ofthe conduit. Then, it may draw the first coolant towards the conduit,where heat is transferred away from the first coolant and cause thecooled first coolant to flow to (and preferably be directed at) the oneor more heat generating components.

Preferably, the pump may be configured provide the first coolant with ahorizontal flow. In other words, the first coolant may be directed in asingle plane around the enclosure, tank or case. This may be parallel toa floor or base of the enclosure and/or in the direction of the flow ofthe second coolant into and out of the enclosure.

In embodiments, the apparatus may further comprise a channel arrangedproximal, close to, adjacent, coaxial, around, enclosing or side-by-sidewith the conduit, the channel having an inlet for receiving the firstcoolant into the channel and an outlet for expelling the first coolantfrom the channel after exchanging heat with the second coolant. Thisprovides a more efficient exchange of heat from the first coolant to thesecond coolant within a heat exchanger.

Preferably, the conduit is located within the channel. This allows thefirst coolant to be forced into close proximity with the second coolantwhen the first coolant is at its highest temperature in the cycle. Thisincreases the cooling efficiency of the heat exchanger.

Optionally, the channel may have a box profile. The channel may beformed from metal, for example.

Preferably, the pump may be in fluid communication with the inlet to thechannel or the outlet of the channel. These components may be linked byan enclosed pipe or channel, for example.

Optionally, the pump may be configured to direct the first coolantparallel or substantially parallel to the flow of the second coolantwithin the conduit. This keeps the first and second coolants in closerproximity improving heat transfer.

Optionally, the conduit (or pipe) may be u-shaped (e.g. having twostraight sides linked by a bend). This may be a pipe or tube bent in themiddle, e.g. at 180 degrees. Other configurations and sizes of theconduit may be used.

Preferably, the enclosure may further comprise an inlet and an outletfor the second coolant. The inlet and outlet are sealed against theenclosure to prevent the first and second coolants from mixing. Theinlet and outlet pass through a wall or side of the case, enclosure ortank.

Optionally, the inlet and the outlet for the second coolant may beadjacent. This makes it easier to connect the inlet and outlet to asystem for circulating the second coolant. The inlet and outlet mayinclude removable connectors and/or flexible hoses.

Optionally, the inlet and the outlet for the second coolant may belocated adjacent to the pump. Alternatively, the inlet and the outletfor the second coolant may be located adjacent to the conduit.

Optionally, the apparatus may further comprise one or more heat sinks inheat communication with the one or more heat generating components. Thisimproves the heat conduction between the heat generating components andthe first coolant. The heat sinks may be metal, for example.

The enclosure may have a rectangular or square cross section, forexample.

Preferably, the one or more heat sinks may have fins arranged parallelto the flow of the first coolant. This reduces disruption in the flow ofthe first coolant within the enclosure and improves the rate at whichheat is removed from heat generating components.

Optionally, the enclosure may further arranged to house one or morepower supplies within the volume. Therefore, the power supplies may alsobe cooled by the first coolant. The power supplies may include externalpower connectors that pass through the enclosure. The power connectorsmay be sealed against leakage of the coolants.

Optionally, the apparatus may further comprise a second pump. Furtherpumps may also be included. Two pumps allow the first coolant tocirculate in different directions further improving the rate at whichheat may be removed.

Optionally, the first pump and the second pump may be arranged eitherside of the conduit. Other configurations may be used. The pumps may bein the same plane.

In some embodiments, the conduit forms part of a heat exchanger unit.Then, a pipe may be configured to direct the first coolant to the heatexchanger unit. The heat exchanger unit may comprise the channelarranged proximal, close to, adjacent, coaxial, around, enclosing orside-by-side with the conduit. The channel inlet may be coupled to thepipe. A second pipe may be coupled to the channel outlet for directingthe (cooled) first coolant to the at least one heat generatingcomponent. The pump is (or pumps are) preferably provided upstream fromthe heat exchanger unit (but might be provided downstream from the heatexchanger unit in some embodiments.

Optionally, the heat exchanger unit further comprises a housingsurrounding the conduit. Then, the housing may have an inlet for firstcoolant to flow through the heat exchanger unit. The heat exchanger unitis preferably positioned at an edge of the volume within the sealableenclosure.

Preferably, the at least one heat generating component is immersed inthe first coolant. The first coolant can fill the enclosure with no airgaps.

Preferably, the first coolant is a liquid (at room temperature).

Preferably, the first coolant is a one phase coolant. In other words,the first coolant may remain in the liquid phase at all stages of itscycle around the enclosure. The apparatus may be advantageouslyconfigured to maintain the first coolant in the one phase.

Optionally, the first coolant may be a two phase coolant. With such acoolant, the liquid may turn to vapour or gas when it contacts a heatgenerating component. The first coolant may then condense when it iscooled within the channel or heat exchanger.

Preferably, the second coolant is water or water based. This provides asafer and more efficient coolant that circulates outside of theenclosure. The secondary coolant may be water based and contain waterand other additives. These may include one or more corrosion inhibitorsand/or bio-growth inhibitors. For example, this may be a mix of 33%(+/−10%) glycol (by volume) in demineralised water.

The heat generating component may be any type of electrical componentand in particular may be a computer component. For example, the heatgenerating electrical component may form part of a CPU or be used fordata storage. There may be more than one heat generating electricalcomponent mounted within the cooling module, and reference to “a” heatgenerating electrical component herein should be interpreted to mean “atleast one” heat generating electrical component.

The volume of the sealable enclosure may be defined by a container (suchas a tank or tray). The container is preferably arranged to house thefirst coolant and one or more heat generating components. Then, thesealable enclosure may be arranged so as to prevent the first coolantfrom leaving the container once the sealable enclosure is sealed. Inother words, the first coolant may be sealed within the container, whichhas no inlet or outlet for the first coolant to leave the container.Heat exchange between the first coolant (in the volume) and the secondcoolant (in the conduit) takes place entirely within the sealableenclosure (that is, the container).

There are a number of benefits in having the first coolant contained(entirely) within the sealable enclosure. Firstly, the pressure of thefirst coolant may be reduced, because it does not leave the container(which would direct it towards to a rank or cabinet infrastructureoutside the apparatus). The first coolant loop may thereby be providedentirely within the container. This makes the first coolant loop smallerthan would otherwise be required (if the first coolant was directedoutside the container) and requires fewer valves, connectors and otherconfigurable parts through which the first coolant may need to flow.This reduces any pressure drop and therefore the resultant operatingpressure.

Secondly, containing the first coolant loop and pump within the sealableenclosure means that the flow rate is individually controlled in eachcontainer. If the pump is external to the sealable enclosure (that is,the container), such as in a rack or cabinet infrastructure withmultiple such sealable enclosures, a single pump or primary coolant loopmay need to balance flow over each sealable enclosure. This ispotentially very difficult to control.

A third issue in providing the first coolant (and any part of the firstcoolant loop) outside of the sealable enclosure (such as in the cabinetinfrastructure) is that any failure (such as blockage, pump failure orleak) affects all of the individual sealable enclosures. Maintaining thefirst coolant within the sealable enclosure (container) may avoid theseissues.

Any of these aspects or individual features of these aspects may be usedtogether or in any combination. For example, the heat exchanger may beused with any of the cooling modules or apparatuses.

BRIEF DESCRIPTION OF THE FIGURES

The present invention may be put into practice in a number of ways andembodiments will now be described by way of example only and withreference to the accompanying drawings, in which:

FIG. 1 shows an exploded view of an example cooling system for heatgenerating components according to a first embodiment, the coolingsystem including a heat exchanger system;

FIG. 2 shows a perspective view of the cooling system of FIG. 1 ;

FIG. 3 shows a further perspective view of the cooling system of FIG. 1rotated by 90 degrees;

FIG. 4 shows a perspective view of the heat exchanger of the coolingsystem of FIG. 1 ;

FIG. 5 shows a schematic diagram in plan view of the cooling system ofFIG. 1 ;

FIG. 6 shows a plan view of the cooling system of FIG. 1 , including anindication of the flow of a secondary coolant;

FIG. 7 shows a plan view of the cooling system of FIG. 1 , including anindication of the flow of a primary coolant;

FIG. 8A shows a perspective view of a further example cooling systemhaving an alternative heat exchanger system;

FIG. 8B shows a different perspective view of the further examplecooling system;

FIG. 9 shows a perspective view of the alternative heat exchanger systemof FIGS. 8A and 8B;

FIG. 10 shows a plan view of the further example cooling system of FIGS.8A and 8B, including an indication of the flow of a primary coolant;

FIG. 11 shows a plan view of the further example cooling system of FIGS.8A and 8B;

FIG. 12 shows an exploded view of an example cooling system for heatgenerating components according to a second embodiment, the coolingsystem including a heat exchanger system;

FIG. 13 shows a perspective view of the cooling system of FIG. 12 ;

FIG. 14 shows a further perspective view of the cooling system of FIG.12 rotated by 90 degrees;

FIG. 15 shows a perspective view of the heat exchanger of the coolingsystem of FIG. 12 ;

FIG. 16 shows a schematic diagram in plan view of the cooling system ofFIG. 12 ;

FIG. 17 shows a plan view of the cooling system of FIG. 12 , includingan indication of the flow of a secondary coolant.

It should be noted that the figures are illustrated for simplicity andare not necessarily drawn to scale. Like features are provided with thesame reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following figures illustrate various aspects and features of acooling system 5 that may be used with one or more heat generatingcomponents. The cooling system 5 shown in FIGS. 1 to 7 may be usedwithin a rack or shelving mounting system but other configurations maybe used, including use as a stand-alone system. The cooling system 5 maytake the form, or dimensions of a blade server, such as a one rack unit19 inch blade (19×1.75 inch or 480 mm×44 mm), for example. Other sizesand racks may be used.

FIG. 1 shows an exploded view of some of the components of the coolingsystem 5. Not all components are shown in this figure, which is inschematic form illustrating the general layout for simplicity.

A rectangular coolant enclosure, tank, case or tray 10 defining a volumethat may be filled with a first or primary coolant, which is preferablya dielectric fluid. This coolant tank is water, gas and/or fluid tightand leak-proof. Dotted line 25 encloses a set of components that bothcool and circulate the first coolant. These components include a heatexchanger 20 and a pair of pumps 30. The heat exchanger 20 cools theprimary coolant using a second or secondary coolant. The pumps 30 drawthe primary coolant through the heat exchanger 20 and around the tank10. This example shows two pumps but a single pump (or more than twopumps) may also be used. This pump or pumps are located within the tank10.

In this configuration two motherboards 40 are shown. This layout maymatch the footprint of a 1U 19″ blade. Components on the motherboards 40include heat generating components that require cooling. Othercomponents 50 are shown schematically in FIG. 1 . These other componentsmay include power supplies, for example. These other components 50 areshown at one end (i.e. a rear end) of the tank 10. The rear end may bethe end of the tray 10, where electrical connectors are mounted. Thismakes it easier to make electrical and power connections to these othercomponents 50 as connectors (not shown in this figure) may be providedat the same end of the tank 10.

FIG. 2 shows a schematic diagram of the same components of the coolingsystem 5 shown in FIG. 1 but located in assembled form within the tank10. The components are substantially arranged in the same plane. FIG. 3shows the cooling system 5, rotated by 90 degrees. An inlet port 70 andoutlet port 75 are shown either side of a centre line (i.e. a long axis)of the tank 10. These ports 70, 75 allow the secondary coolant to enterand exit the tank 10. While the secondary coolant is within the tank itflows through the heat exchanger within a conduit such as a pipe or tube(not shown). Preferably, the conduit is formed from a good heatconductor such as a metal so that heat may be easily exchanged betweenthe primary coolant and the secondary coolant, which is maintained orcooled to a temperature below that of the primary coolant drawn into theheat exchanger. This cooled primary coolant is directed over one or moretemperature generating components 60 on the motherboard 40. Examples ofhigh temperature components are processors and memory although othercomponents may also be placed on the motherboard 40 and cooled.

The flow of the primary coolant may be customised to suit different hightemperature component positions and configurations. Heat sinks (notshown in this figure) may also be located on or near to heat generatingcomponents 60. The heat sinks on the heat generating components may havefins or baffles that are placed parallel to the flow of the primarycoolant to improve circulation.

FIG. 4 shows in greater detail the set of components or heat exchangersystem 25 that both cools and circulates the first coolant. Pumps 30(e.g. impeller pumps) draw, direct or suck the primary coolant in to theheat exchanger 20 through an aperture or void 120 at one end. Theprimary coolant is forced or flows along a channel or duct where itsurrounds the conduit that contains the cooler secondary coolant. Theprimary coolant flows along connector or pump pipes 110, which connectthe channel to the pumps 30.

The connector pipes 110 take the primary coolant from the heat exchanger20 to the pumps 30. The pumps are configured to draw equal amounts ofcoolant on each side. As there are no gaps in the connector pipes 110then the primary coolant is pulled through the connector pipes 110 andheat exchanger 20 by the pumps 30. In this example two pumps 30 are usedbut different number of pumps may also be used.

The primary coolant is pumped out of nozzles 100 towards the heatgenerating components (not shown in this figure). As the primary coolanttravels through the channel it comes into contact with the conduit ortube carrying the cooler secondary coolant. This cools the primarycoolant. The channel forces the primary coolant against the secondarycoolant conduit ensuring that more coolant comes into contact, whichincreases the rate (and efficiency) at which the primary coolant iscooled.

The heat exchanger system 25 exchanges heat between the primary andsecondary coolant. Additional components (not shown in this figure) mayinclude heat sinks, cold plates and/or heat pipes.

The pumps 30 may be positioned or configured to direct the primarycoolant over the high temperature or heat generating components 60. Thisconfiguration may be customised for different motherboards 40 or heatgenerating components 60. Different pump configurations, sizes andquantities may be used.

The primary coolant is sucked or drawn into the heat exchanger 20 fromits aperture 120. The primary coolant is at its hottest temperature atthis point. The primary coolant cools as it is sucked or flows down theheat exchanger channel.

FIG. 5 shows a plan view in schematic form of the various components ofthe cooling system 5. This view shows the channel of the heat exchanger20 extending down the centre of the tank 10, with the aperture locatedtowards but not reaching the end of the tank 10 distal to its rear end.The pumps 30 and nozzles 100 are arranged on either side of the heatsink. In this example, the cooling system 5 is substantially symmetricalalong its centre or long axis.

FIG. 6 illustrates schematically the flow 200 of the secondary coolantthrough the conduit within the heat exchanger 20. The conduit may takethe form or a u-tube (e.g. of circular profile or cross section) and soflows substantially parallel with the channel of the heat exchanger 20from the inlet 70 towards the aperture 120 of the channel where it makesa sharp turn to return back towards the outlet 75. During this passage,the secondary coolant will warm up and remove heat from the primarycoolant. Therefore, the secondary coolant will emerge from the outlet 75at a higher temperature than it enters the inlet 70. The secondarycoolant may itself be cooled using passive or active cooling, such as aheat exchanger, heat pump or cooler. Preferably, no active chiller isrequired as the secondary coolant's volume, flow and external radiationcan be configured to return the secondary coolant to the cooling system5 at a temperature low enough to sufficiently cool the primary coolant(i.e. to avoid thermal damage to the heat generating components 60). Thesecondary coolant may be shared between multiple tanks 10, which may beconfigured for flow of the secondary coolant in series, parallel or acombination thereof. An additional pump and controller (or multiplepumps and/or controllers), not shown, may be provided for the flow ofthe secondary coolant.

FIG. 7 shows the flow 310 of the primary coolant as it circulates thetank 10. The pump (or pumps) 30 draw the primary coolant into the heatexchanger channel where it cools. This is achieved by pushing or forcingthe primary coolant out of each pump 30. The primary coolant is at itshottest at the aperture 120. As it passes through the heat exchanger 20the primary coolant cools and is at its coldest at the point marked 320.Heat has been transferred to the secondary coolant within the heatexchanger 25. The primary coolant is directed out of nozzles 100 in thedirection of the heat generating components 60 on the motherboards 40.Arrows 310 indicate the primary coolant passing over and around orspreading over the heat generating components 60, where this heat ispicked up and removed by the primary coolant. Where heat sinks or finsare mounted on or close to the heat generating components 60 (or atother locations within the enclosure 10) then the flow of primarycoolant from the nozzles 100 may be arranged parallel to any fins on theheat sinks. The cycle repeats with the primary coolant again enteringthe aperture 120.

The system may be configured to allow single phase (i.e. liquid)immersion cooling of the electrical components and any componentsmounted within the enclosure. Heat is removed from the vicinity of theheat generating electrical components generally by conduction but alsoby convection. In some circumstances, the cooling module may beconfigured to allow two-phase cooling. In two-phase cooling, heatgenerated by the electrical components causes the coolant liquid to boiland evaporate to a vapour or gas, which then condenses (i.e. at the heatexchanger) so as to remove heat from the cooling module.

Various electrical and power connectors may be provided to couple withthe components or motherboard or motherboards within the volume of theenclosure. These may include a power plug, socket or other connectors.Power and/or data inputs may be arranged at the wall of the coolingmodule so as to allow entry of an electrical and/or data connection intothe cooling module from external power or data sources. In some cases,these inputs may be arranged at a rear plate or back plate of thecooling module, for instance on the same face as any data connectionsand or the inlet and outlet of the secondary coolant.

The pump or pumps may alternatively be located at or close to theaperture 120 (or hotter end) of the channel rather than at the coolerend. FIGS. 8A, 8B, 9, 10 and 11 illustrate this alternative arrangementin more detail. FIGS. 8A and 8B show different perspective views of thisarrangement, where the pump or pumps draw or suck the hot primarycoolant (i.e. after picking up heat from the heat generating components)into the heat exchanger. This is an alternative to directing the cooledprimary coolant out of the heat exchanger and on to the heat generatingcomponents causing hotter or hottest primary coolant to be drawn into orsucked into the aperture of the heat exchanger.

FIG. 9 shows a perspective view of an alternative heat exchanger system25′ found within the alternative cooling system 5′. The other componentsare substantially the same as previously described. In general, the pumpor pumps 30′ each have a pump inlet 400 configured to draw the primarycoolant into the heat exchanger channel 20. In this arrangement, ratherthan an aperture open to the volume holding the primary coolant, thechannel 20 is attached to an outlet or outlets of a pump or pumps 30′ toform a sealed coupling 410. FIG. 9 shows this sealed coupling 410 to bein the form of two pipes or tubes but a single tube (or otherarrangement) may be used instead. The pump inlets 400 are shown at rightangles to the channel 20 but other angles (including parallel) may beused.

Nozzles 100′ direct the primary coolant over the motherboards 40 and anyheat generating components 60 are provided in this arrangement. However,these nozzles 100′ are no longer required to be attached directly to thepump or pumps 30′. These nozzles 100′ are connected to the colder end(in use) of the heat exchanger via connector pipes 110′.

FIG. 10 illustrates schematically the flow of the primary coolant withinthis alternative arrangement cooling system 25′. The coolant flow issubstantially similar to that of the other arrangement (previouslydescribed) cooling system 25. A difference is that the primary coolantis pushed around the system 5′ by the pump or pumps 30′ at a differentpoint in the cycle or flow. FIG. 11 shows a top view of the coolingsystem 25′. This arrangement uses a similar flow, control and set ofcomponents for the secondary coolant as that described previously withthe first arrangement.

With this arrangement the pump or pumps 30′ are located at the distalend of the tank 10 opposing the rear wall. The primary coolant istherefore pushed through the heat exchanger 20 rather than sucked ordrawn through it. This can provide a more effective mechanism.Therefore, the pumps 30′ don't direct the flow of the primary coolantonto the motherboards 40 or heat generating components 60 as this isprovided indirectly by the nozzles 100′.

A variety of coolant fluids or liquids may be used as the primary and/orsecondary coolants. Coolant liquids will be liquid at room temperature.Coolant liquids for single phase immersion cooling will be liquid undernormal operating temperatures for the heat generating electricalcomponent. However, those coolants used or sealed within the enclosurefor two-phase immersion cooling should evaporate into a gas (i.e. have aboiling point) at normal operating temperatures of the heat generatingelectrical component, but be liquid at slightly lower temperatures.Examples of suitable coolant liquids (preferably, for the primarycoolant) include natural oils, synthetic oils, fluoro-octanes (forinstance Fluorinert™), hydrofluoroether, HFE (for instance Novec™),hydrofluorolefin, HFO (for instance Vertrel Sinara™), perfluoroketone,PFK (for instance by Novec™), or perfluoropolyether, PFPE (for instanceSolvay Galden™). However, this list is not exhaustive, and other coolantliquids may be used within the present invention.

The enclosure may be formed from any suitable material including but notlimited to metal, steel and/or aluminium.

As will be appreciated by the skilled person, details of the aboveembodiment may be varied without departing from the scope of the presentinvention, as defined by the appended claims.

For example, a different number of pumps may be used. In use theenclosure has been described as operating horizontally but otherconfigurations (e.g. vertical) may be used. Whilst the conduit in whichthe secondary coolant flows has been described as a u-tube, otherconfigurations and flows may be used. Furthermore, different heatexchanger system configurations may be used.

Further drawings, as described below, illustrate various aspects andfeatures of a cooling system 5″ according to a second embodiment thatmay be used with one or more heat generating components. The details ofthe cooling system 5″ shown in FIGS. 12 to 17 are similar, but varyslightly from those shown with respect to the cooling systems 5 and 5′shown in FIGS. 1 to 11 . Where the same components as used in the firstembodiment are shown, identical reference numerals have been indicated.A variation in the positioning and/or arrangement of the component hasbeen indicated by a mark after the reference numeral, for example withreference to cooling system 5″. An understanding of most of thisembodiment can be gained from the explanation provided above withreference to FIGS. 1 to 11 . The skilled person will understand that,where compatible, the features described with reference to otherembodiments may also be applied to the cooling system 5″ shown in FIGS.12 to 17 .

FIG. 12 shows an exploded view of some of the components of the coolingsystem 5″. This is generally similar to that shown in FIG. 1 , but withsome changes to the layout of a heat exchanger 20″ and a pair of pumps30″. Dotted line 25″ encloses a set of components that both cool andcirculate the first coolant in this second embodiment. The heatexchanger 20″ is located at an edge of the tank 10 and provides theconduit (not shown, as it is within the heat exchanger 20″) throughwhich the secondary coolant is arranged to flow. The pumps 30″ areconfigured to draw the primary coolant through the heat exchanger 20″,particularly though a channel within the heat exchanger 20″ that isproximal to the conduit in which the secondary coolant is arranged toflow, such that heat is transferred from the channel to the conduit) andaround the tank 10. The secondary coolant conduit therefore provides afluid-tight seal between the primary coolant and the secondary coolant.This is especially effective when the primary coolant enters the heatexchanger 20″ and surrounds the secondary coolant conduit.

FIG. 13 shows a schematic diagram of the same components of the coolingsystem 5″ shown in FIG. 12 but located in assembled form within the tank10. It will be seen from this drawing that the location of othercomponents 50 (typically power supplies) may be adjusted in comparisonwith the first embodiment, in view of the change of layout. FIG. 14shows the cooling system 5″, rotated by 90 degrees.

FIG. 15 shows in greater detail the set of components or heat exchangersystem 25″ that both cools and circulates the first coolant in thisembodiment (which is in fact more similar to the variant shown in FIG. 9than that depicted in FIG. 4 ). Pumps 30″ draw, direct or suck theprimary coolant in to the heat exchanger 20″ through respective pumpinlets 400 at each pump 30″. The primary coolant is at its hottesttemperature at this point. The primary coolant flows along a pipe orduct 420 to the heat exchanger 20″ throughout inlet 410. The primarycoolant is cooled within the heat exchanger 20″ and then flows alongconnector or pump pipes 110″, which release the primary coolant throughnozzles 100″. The primary coolant is pumped out of nozzles 100″ towardsthe heat generating components (not shown in this figure). FIG. 16 showsa plan view in schematic form of the various components of the coolingsystem 5″. Other configurations of the pumps 30″, duct 420, heatexchanger 20″ and outlets 100″ are possible.

FIG. 17 illustrates schematically the flow 450 of the primary coolantthrough the pumps 30″, duct 420, heat exchanger 20″ and within the tank10. This differs slightly from FIG. 6 , which shows the flow of thesecondary coolant. The primary coolant is drawn through the pumps 30″into the duct 420, until it reaches the heat exchanger 20″. There, theheat carried by the primary coolant is transferred to the secondarycoolant. The cooled primary coolant is pumped out and passes over theheat generating components to receive further heat, until being drawnback through the pumps 30″.

Many combinations, modifications, or alterations to the features of theabove embodiments will be readily apparent to the skilled person and areintended to form part of the invention. Any of the features describedspecifically relating to one embodiment or example may be used in anyother embodiment by making the appropriate changes.

The invention claimed is:
 1. An electronic system, comprising: a rack; aplurality of liquid submersion cooled electronic devices disposed in avertical array on the rack, wherein each of the liquid submersion cooledelectronic devices includes: a liquid tight tray having a bottom walland side walls defining an interior space, and an at least partiallyopen top opposite the bottom wall; a removable cover over the at leastpartially open top; at least one heat generating electronic componentdisposed within the interior space; a single phase dielectric coolingliquid in the interior space, the single phase dielectric cooling liquidpartially or fully submerging and in direct contact with the at leastone heat generating electronic component; a pump having a pump inlet influid communication with the interior space, and a pump outlet; and aheat exchanger extending into the interior space, the heat exchangerhaving a heat exchanger inlet connected by a pipe to the pump outlet ofthe pump, and a heat exchanger outlet in fluid communication with theinterior space, wherein the pump is configured to direct the singlephase dielectric cooling liquid into the heat exchanger; and a secondarycooling fluid loop in fluid communication with each heat exchanger thatsupplies a secondary cooling liquid to each heat exchanger such thatheat is exchanged between the single phase dielectric cooling liquidcoolant of each of the liquid submersion cooled electronic devices andthe secondary cooling liquid.
 2. The electronic system of claim 1,wherein for each of the liquid submersion cooled electronic devices, theat least one heat generating electronic component comprises a pluralityof heat generating electronic components within the interior space, andwherein the plurality of heat generating electronic components comprisea plurality of data storage devices, a plurality of power supplies, or aplurality of processors.
 3. The electronic system of claim 1, whereineach of the liquid submersion cooled electronic devices is a server.